Series-parallel hybrid power transmission system of tractor and control method

Abstract

A kind of series-parallel hybrid power transmission system and control method of tractor belongs to tractor power transmission field, including power system, coupling device, transmission, transfer case, central transmission mechanism, final drive mechanism and power output transmission mechanism;Engine and motor I are mechanically connected, motor I output shaft and motor II output shaft form power coupling via coupling device, the mode switch of coupling device is connected by respectively with planetary gear set planetary carrier and mode switching device output shaft clutch, realize motor I output shaft and motor II output shaft coupling transmission, or the mode switching of motor II output shaft independent transmission, ensure that system can dynamically adjust power flow path according to agricultural demand, realize high-power operation engine mechanical direct drive, small power light load operation engine speed and vehicle driving demand decoupling, give consideration to tractor heavy load operation and high-speed scene of whole scene power demand, so that whole machine can give consideration to high mobility operation and optimal energy utilization rate under various complex working conditions.

Description

Technical Field

[0001] This invention belongs to the field of tractor power transmission, specifically a hybrid power transmission system and control method for a series-parallel hybrid tractor. Background Technology

[0002] As a core power source in modern agricultural production, tractors exhibit significant complexity and polarization in their operating conditions. During heavy-duty field operations such as plowing and rotary tilling, tractors require sustained output of substantial traction, maintaining a relatively stable speed, typically in a low-speed range, and often needing to provide stable power to implements via the power take-off axis. However, during field relocation, unloaded transport, or road travel, tractors bear lighter loads, and their speed varies more dramatically, necessitating a continuously variable transmission (CVT) system to improve operational efficiency.

[0003] Traditional tractors typically use a single diesel engine paired with a multi-speed mechanical gearbox and transfer case. To balance the conflicting demands of low-speed heavy-load and high-speed light-load operations, traditional gearboxes have to be designed with extremely complex gear structures, resulting in a bulky transmission system, high manufacturing costs, cumbersome shifting operations, and a strong sense of jerkiness. Existing hybrid tractor technologies are mainly divided into series and parallel types. While series hybrid tractors achieve continuously variable transmission (CVT), energy requires a secondary "mechanical-electrical-mechanical" conversion during heavy-load operations, resulting in a significantly lower overall efficiency than direct mechanical drive, making it unsuitable for prolonged heavy traction work. Simpler parallel hybrid solutions typically only add a motor before the gearbox, failing to effectively address the technical bottleneck of strong coupling between the power take-off shaft speed and vehicle speed. That is, when maintaining a constant power take-off shaft speed, the vehicle speed cannot be flexibly adjusted; furthermore, this type of solution still retains a complex rear axle gearbox and mechanical front drive shaft, limiting the degree of structural optimization. Therefore, there is an urgent need to develop a new hybrid power transmission system that can combine the speed regulation flexibility of electric drive with the high efficiency of mechanical drive, while greatly simplifying the mechanical gearbox structure, realizing direct mechanical drive of high-power working engine, and decoupling the speed of low-power working engine from vehicle speed. Summary of the Invention

[0004] The purpose of this invention is to solve the problem of strong coupling between the power output shaft speed and the vehicle speed, and to provide a hybrid power transmission system and control method for a series-parallel hybrid tractor.

[0005] The technical solution adopted by the present invention to solve the above-mentioned technical problems is: a hybrid power transmission system for a tractor, comprising a power system, a coupling device, a central transmission mechanism, and a power output transmission mechanism; the central transmission mechanism and the power output transmission mechanism are connected to the coupling device and are respectively used to output traction power and rotational power; the power system includes an engine, motor I, and motor II, the engine is mechanically connected to the output shaft of motor I, and the output shaft of motor I is connected to the coupling device and the power output transmission mechanism, so that the engine and motor I can provide power independently or in a parallel coupled drive manner.

[0006] The coupling device includes a drive gear on motor I shaft, a drive gear on motor II shaft, a planetary gear set mechanism, a series mode gear transmission mechanism, and a mode switcher; the drive gear on motor I shaft and the drive gear on motor II shaft are mechanically connected to the output shaft of motor I and the output shaft of motor II, respectively.

[0007] The driving gear of motor I shaft meshes with the planetary gear ring in the planetary gear mechanism, and the driving gear of motor II shaft meshes with the driven gear of motor II shaft connected to the sun gear of the planetary gear set, so that the output shaft of motor I and the output shaft of motor II form a power coupling through the planetary gear set; the planetary carrier of the planetary gear set is connected to the output shaft of the mode switching device through the mode switcher, and the output shaft of the mode switching device is connected to the central transmission mechanism.

[0008] The mode switcher is connected to a series mode output gear on one side of the output shaft of the mode switching device. The driven gear of the motor II shaft is connected to the series mode output gear through a series mode gear transmission mechanism, forming an independent power transmission path between the output shaft of the motor II and the output shaft of the mode switching device.

[0009] The mode switcher is a dual-clutch structure, which can achieve mode switching by coupling the output shaft of motor I with the output shaft of motor II, or by independently driving the output shaft of motor II, through clutch connection with the planetary carrier of the planetary gear set and the output shaft of the mode switcher respectively.

[0010] The aforementioned series mode gear transmission mechanism includes a series mode input gear and a series mode intermediate gear. The series mode input gear meshes with the driven gear of motor II shaft and is mechanically connected to the series mode intermediate gear. The series mode intermediate gear meshes with the series mode output gear.

[0011] The motor II is equipped with an electromagnetic locker, which can lock the output shaft of motor II, so that the output shaft of motor I can independently drive the planetary gears of the planetary gear set to transmit power to the planetary carrier and mode switch via the drive gear of motor I shaft and the planetary gear ring.

[0012] The output shaft of motor I passes through the output shaft of motor II, so that the engine, motor I and motor II are arranged in a straight line.

[0013] The coupling device is connected to the central transmission mechanism via a gearbox and a transfer case; the gearbox includes a first shaft input gear, a two-speed synchronizer, a first shaft output gear, a gearbox output shaft, a second shaft output gear, and a second shaft input gear; the first shaft input gear is mechanically connected to the output shaft of the mode switching device and meshes with the second shaft input gear; the first shaft output gear, the first shaft input gear, and the gearbox output shaft connected to the transfer case are connected via the two-speed synchronizer; the first shaft output gear meshes with the second shaft output gear; the second shaft input gear is mechanically connected to the second shaft output gear, realizing the speed change transmission from the first shaft input gear to the first shaft output gear.

[0014] The transfer case includes a transfer case input gear, a transfer case intermediate gear, a transfer case clutch, a transfer case front output shaft, and a transfer case output gear; the transfer case input gear is mechanically connected to the transmission output shaft, the transfer case intermediate gear meshes with both the transfer case input gear and the transfer case output gear, and the transfer case output gear is connected to the transfer case front output shaft via the transfer case clutch.

[0015] The central transmission mechanism includes a main reducer drive gear, a main reducer driven gear, a right half-shaft, a differential lock, a differential, and a left half-shaft; the main reducer drive gear is mechanically connected to the transmission output shaft and meshes with the main reducer driven gear; the main reducer driven gear is mechanically connected to the differential; the right half-shaft and the left half-shaft are mechanically connected through the differential lock and are respectively mechanically connected to the differential.

[0016] The central transmission mechanism is connected to the wheel via a final transmission mechanism, which includes a final transmission ring gear, a wheel axle, a final transmission planetary carrier, final transmission planet gears, and a final transmission sun gear. The final transmission sun gear is connected to the central transmission mechanism, the final transmission ring gear is mechanically connected to the housing, and the final transmission planet gears mesh with the final transmission sun gear and the final transmission ring gear, respectively. The final transmission planetary carrier, which is connected to the final transmission planet gears, is mechanically connected to the wheel via the wheel axle.

[0017] The power output transmission mechanism includes a power output transmission clutch, a first gear on a first power output transmission shaft, a second gear on a first power output transmission shaft, a second gear on a second power output transmission shaft, a power output transmission output shaft, a power output transmission synchronizer, and a first gear on a second power output transmission shaft. The first gear on the first power output transmission shaft and the second gear on the first power output transmission shaft are mechanically connected and connected to the output shaft of motor I via the power output transmission clutch. The second gear on the second power output transmission shaft meshes with the second gear on the first power output transmission shaft, and the first gear on the second power output transmission shaft meshes with the first gear on the first power output transmission shaft. The second gear on the second power output transmission shaft, the power output transmission output shaft, and the first gear on the second power output transmission shaft are connected via the power output transmission synchronizer.

[0018] A control method for a hybrid power transmission system of a series-parallel hybrid tractor is disclosed. During the operation of the hybrid tractor, the load-side working mode is determined based on the output states of traction power and rotational power, combined with acquired torque signals, speed signals, and the stored power of the energy storage unit. When the total power demand exceeds the lower limit of the economic range of the total power demand of the diesel engine mechanical connection, the traction mode is determined based on the speed of the wheels. When the speed of the wheels is within the upper and lower limits of the economic range of the vehicle speed of the diesel engine mechanical connection, a parallel torque coupling traction mode in which the engine and motor I jointly output power or an independent engine traction mode is adopted. When the speed of the wheels exceeds the upper and lower limits of the economic range of the vehicle speed of the diesel engine mechanical connection, a parallel speed coupling traction mode in which the engine and motor II jointly output power or a series-parallel coupling traction mode in which the engine, motor I, and motor II jointly output power is adopted.

[0019] The beneficial effects of this invention are:

[0020] 1. Both Motor I and Motor II can be coupled to the engine for transmission. Through the state switching of the coupling device and its mode switcher, the torque coupling, speed coupling and power coupling between multiple power sources such as the engine, Motor I and Motor II can be flexibly switched, taking into account the power needs of the tractor in all scenarios of heavy-duty operation and high-speed transfer.

[0021] 2. By integrating the advantages of series, parallel, and hybrid architectures, intelligent mode switching of multiple power sources across the entire speed range is achieved. This design ensures that the system can dynamically adjust the power flow path according to different agronomic needs, realizing direct mechanical drive of the high-power operating engine and decoupling the power of the low-power light-load operating engine from the vehicle's drive requirements. It takes into account the power needs of tractors in all scenarios, including heavy-load operation and high-speed transfer, enabling the entire machine to maintain high mobility and optimal energy utilization under various complex working conditions.

[0022] 3. The mode switcher of the coupling device can directly realize the direct drive between motor II and the walking system without the need to install a locker at the planetary gear set. Structurally, it avoids the damage caused by the impact of locker switching under high load conditions of tractor and improves the heavy load reliability of the transmission system.

[0023] 4. The parallel or hybrid coupling path achieved by using planetary gears ensures that power can be transmitted through mechanical direct drive within the heavy load speed range. This not only guarantees the highest transmission efficiency of the system under heavy load, but also, in conjunction with the "peak shaving and valley filling" function of the energy storage unit, realizes stepless speed change in the working range and improves the continuity of power transmission.

[0024] 5. Both Motor I and Motor II can switch between generator mode and power output mode, flexibly changing the motor operating mode according to different working conditions. Utilizing the extremely fast dynamic response characteristics of the motors, the system can quickly regulate the energy storage unit to release energy when soil resistance changes abruptly, thereby compensating for the drive torque in real time. This power support mechanism effectively suppresses transient fluctuations in the engine, significantly improving the tractor's power stability and operational smoothness under heavy load conditions.

[0025] 6. By achieving deep decoupling between the engine and power output torque and wheel power, the system ensures that the engine provides a stable working power flow at a constant speed. The vehicle speed is independently, continuously, and precisely regulated by the electric motor, solving the problem of speed being limited by engine speed and significantly improving the quality of precision operations. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the power transmission system of the hybrid tractor of the present invention.

[0027] Figure 2 This is a schematic diagram of the power system of the present invention.

[0028] Figure 3 This is a schematic diagram of the coupling device of the present invention.

[0029] Figure 4 This is a schematic diagram of the transmission structure of the present invention.

[0030] Figure 5 This is a schematic diagram of the transfer case of the present invention.

[0031] Figure 6 This is a schematic diagram of the central transmission mechanism of the present invention.

[0032] Figure 7 This is a schematic diagram of the final transmission mechanism of the present invention.

[0033] Figure 8 This is a schematic diagram of the power output transmission mechanism of the present invention.

[0034] Figure 9 This is a schematic diagram of the control structure of the hybrid power transmission system of the tractor of the present invention.

[0035] Figure 10 This is a schematic diagram of the power flow in the pure electric traction mode of the power transmission system of the present invention.

[0036] Figure 11 This is a schematic diagram of the power flow in the independent traction mode of the engine in the power transmission system of the present invention.

[0037] Figure 12 This is a schematic diagram of the power flow in the series coupling traction mode of the power transmission system of the present invention.

[0038] Figure 13 This is a schematic diagram of the power flow in the parallel torque coupling traction mode of the power transmission system of the present invention.

[0039] Figure 14 This is a schematic diagram of the power flow in the parallel speed coupling traction mode of the power transmission system of the present invention.

[0040] Figure 15 This is a schematic diagram of the power flow in the hybrid coupling traction mode of the power transmission system of the present invention.

[0041] Figure 16 This is a schematic diagram of the power flow in the energy recovery mode of the power transmission system of the present invention.

[0042] Figure 17 This is a schematic diagram of the power flow in the pure electric drive mode of the power transmission system of the present invention.

[0043] Figure 18 This is a schematic diagram of the power flow in the engine-independent drive mode of the power transmission system of the present invention.

[0044] Figure 19 This is a schematic diagram of the power flow in the parallel coupled drive mode of the power transmission system of the present invention.

[0045] Figure 20 This is a flowchart of the control method for the power transmission system of the hybrid tractor of the present invention.

[0046] The diagram is labeled as follows: 1. Power system; 101. Engine; 102. Mechanical flywheel; 103. Motor I; 104. Energy storage unit; 105. Motor II; 106. Output shaft of Motor II; 107. Output shaft of Motor I.

[0047] 2. Coupling device, 201. Motor II shaft drive gear, 202. Motor I shaft drive gear, 203. Planetary gear ring, 204. Mode switcher, 205. Series mode output gear, 206. Mode switcher output shaft, 207. Series mode intermediate gear, 208. Planetary gear carrier, 209. Planetary gear sun gear, 210. Series mode input gear, 211. Motor II shaft driven gear, 212. Planetary gear.

[0048] 3. Gearbox; 301. First shaft input gear; 302. Two-speed synchronizer; 303. First shaft output gear; 304. Gearbox output shaft; 305. Second shaft output gear; 306. Second shaft input gear.

[0049] 4. Transfer case; 401. Transfer case input gear; 402. Transfer case intermediate gear; 403. Transfer case clutch; 404. Transfer case front output shaft; 405. Transfer case output gear.

[0050] 5. Central transmission mechanism; 501. Main reducer drive gear; 502. Main reducer driven gear; 503. Right half shaft; 504. Differential lock; 505. Differential; 506. Left half shaft.

[0051] 6. Final drive mechanism, 601. Final drive ring gear, 602. Wheel axle, 603. Final drive planetary carrier, 604. Final drive planetary gears, 605. Final drive sun gear;

[0052] 7. Wheels;

[0053] 8. Power output transmission mechanism; 801. Power output transmission clutch; 802. First gear of first shaft of power output transmission; 803. Second gear of first shaft of power output transmission; 804. Second gear of second shaft of power output transmission; 805. Output shaft of power output transmission; 806. Synchronizer of power output transmission; 807. First gear of second shaft of power output transmission.

[0054] 9. Control system; 901. Machine controller; 902. Distribution box; 903. Engine controller; 904. Transmission system controller; 905. Motor I controller; 906. Motor II controller; 907. Energy management unit. Detailed Implementation

[0055] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. The specific contents listed in the following embodiments are not limited to the technical features necessary to solve the technical problem of the present invention. Furthermore, the listed embodiments are merely a part of the present invention, and not all embodiments.

[0056] like Figure 1As shown, the hybrid powertrain system of the series-parallel hybrid tractor includes a power system 1, a coupling device 2, a transmission 3, a transfer case 4, a central drive mechanism 5, a final drive mechanism 6, wheels 7, a power output transmission mechanism 8, and a control system 9. The power system 1 employs multiple power sources, and its output power is coupled via the coupling device 2. One power output from the coupling device 2 is transmitted to the power output transmission mechanism 8 to output rotational power to drive the tractor implements; the other output power is transmitted via the transmission 3 and the transfer case 4 to the central drive mechanism 5 to output traction power to the final drive mechanism 6 to drive the tractor forward.

[0057] like Figure 2 As shown, the power system 1 includes an engine 101, a mechanical flywheel 102, a motor I 103, an energy storage unit 104, a motor II 105, an output shaft 106 for motor II, and an output shaft 107 for motor I. The engine 101, mechanical flywheel 102, and motor I 103 are mechanically connected via the output shaft 107, enabling the engine 101 and motor I 103 to provide power independently or in a parallel coupled drive configuration. Motor II 105 is mechanically connected to the output shaft 106. The energy storage unit 104 can be composed of a power battery, a supercapacitor, or both. Both motor I 103 and motor II 105 have two operating modes: power generation and power output. Depending on the operating conditions, they can obtain electrical energy from the power battery to provide driving force, or they can switch to power generation mode to store electrical energy in the power battery. The output shaft 107 of motor I passes through the output shaft 106 of motor II. The engine 101, motor I 103 and motor II 105 are arranged in a straight line, making the power transmission system structure more compact and saving space.

[0058] like Figure 3As shown, the coupling device 2 includes a motor I shaft drive gear 202, a motor II shaft drive gear 201, a planetary gear ring 203, a mode switcher 204, a series mode output gear 205, a mode switcher output shaft 206, a series mode intermediate gear 207, a planetary gear carrier 208, a planetary gear sun gear 209, a series mode input gear 210, a motor II shaft driven gear 211, and planetary gears 212. The motor I shaft drive gear 202 and the motor II shaft drive gear 201 are mechanically connected to the motor I output shaft 107 and the motor II output shaft 106, respectively, to receive power input from the power system 1. The planetary gear mechanism, composed of the planetary gear ring 203, the planetary gear carrier 208, the planetary gear sun gear 209, and the planetary gears 212, is the core component for achieving power coupling. The driving gear 202 of motor I shaft meshes with the planetary gear ring 203 in the planetary gear mechanism, and the driving gear 201 of motor II shaft meshes with the driven gear 211 of motor II shaft connected to the sun gear 209 of the planetary gear set, so that the output shaft 107 of motor I and the output shaft 106 of motor II form a power coupling through the planetary gears 212 of the planetary gear set. The planetary carrier 208 of the planetary gear set 212 is connected to the output shaft 206 of the mode switching device through the mode switcher 204. The output shaft 206 of the mode switching device is connected to the central transmission mechanism 5 for outputting traction power.

[0059] The motor II 105 is equipped with an electromagnetic locker that can lock the output shaft 106 of the motor II, so that the output shaft 107 of the motor I can independently drive the planetary gears 212 of the planetary gear set to transmit power to the planetary carrier 208 and the mode switcher 204 via the drive gear 202 of the motor I shaft and the planetary gear ring 203.

[0060] like Figure 2 and 3 As shown, the serial mode input gear 210 and the serial mode intermediate gear 207 form a serial mode gear transmission mechanism that independently transmits power from the output shaft 106 of motor II to the output shaft 206 of the mode switching device. The serial mode input gear 210 meshes with the driven gear 211 of the motor II shaft and is mechanically connected to the serial mode intermediate gear 207. A serial mode output gear 205 is mechanically connected to one side of the mode switcher connected to the output shaft 206 of the mode switching device, and the serial mode intermediate gear 207 meshes with the serial mode output gear 205. The driven gear 211 of the motor II shaft is connected to the serial mode output gear 205 through the serial mode gear transmission mechanism, forming an independent power transmission path between the output shaft 106 of motor II and the output shaft 206 of the mode switching device.

[0061] The mode switcher 204 is a dual-clutch structure. The clutches on both sides are respectively connected to the planetary gear carrier 208 and the output shaft 206 of the mode switcher. By controlling the engagement or disengagement of the clutches on both sides, the mode switching of coupled transmission between the output shaft 107 of motor I and the output shaft 106 of motor II, or independent transmission of the output shaft 106 of motor II can be flexibly realized.

[0062] like Figure 4 As shown, the transmission 3 includes a first shaft input gear 301, a two-speed synchronizer 302, a first shaft output gear 303, a transmission output shaft 304, a second shaft output gear 305, and a second shaft input gear 306. The first shaft input gear 301 is mechanically connected to the output shaft 206 of the mode switching device and meshes with the second shaft input gear 306. The first shaft output gear 303, the first shaft input gear 301, and the transmission output shaft 304 connected to the transfer case 4 are connected by the two-speed synchronizer 302. The first shaft output gear 303 meshes with the second shaft output gear 305. The second shaft input gear 306 is mechanically connected to the second shaft output gear 305, thereby realizing the speed change transmission from the first shaft input gear 301 to the first shaft output gear 303.

[0063] like Figure 5 As shown, the transfer case 4 includes a transfer case input gear 401, a transfer case intermediate gear 402, a transfer case clutch 403, a transfer case front output shaft 404, and a transfer case output gear 405; the transfer case input gear 401 is mechanically connected to the transmission output shaft 304, the transfer case intermediate gear 402 meshes with the transfer case input gear 401 and the transfer case output gear 405 respectively; the transfer case output gear 405 is connected to the transfer case front output shaft 404 through the transfer case clutch 403.

[0064] like Figure 6 As shown, the central transmission mechanism 5 includes a main reducer drive gear 501, a main reducer driven gear 502, a right half-shaft 503, a differential lock 504, a differential 505, and a left half-shaft 506. The main reducer drive gear 501 is mechanically connected to the transmission output shaft 304 and meshes with the main reducer driven gear 502. The main reducer driven gear 502 is mechanically connected to the differential 505. The right half-shaft 503 and the left half-shaft 506 are mechanically connected through the differential lock 504 and are respectively mechanically connected to the differential 505.

[0065] like Figure 7As shown, the final drive mechanism 6 includes a final drive ring gear 601, a wheel axle 602, a final drive planetary carrier 603, final drive planetary gears 604, and a final drive sun gear 605; the final drive sun gear 605 is connected to the central drive mechanism 5, the final drive ring gear 601 is mechanically connected to the housing, and the final drive planetary gears 604 mesh with the final drive sun gear 605 and the final drive ring gear 601 respectively; the final drive planetary carrier 603, which is connected to the final drive planetary gears 604, is mechanically connected to the wheel 7 through the wheel axle 602.

[0066] like Figure 8 As shown, the power output transmission mechanism 8 includes a power output transmission clutch 801, a first gear 802 of a first power output transmission shaft, a second gear 803 of a first power output transmission shaft, a second gear 804 of a second power output transmission shaft, a power output transmission output shaft 805, a power output transmission synchronizer 806, and a first gear 807 of a second power output transmission shaft. The first gear 802 and the second gear 803 of the first power output transmission shaft are mechanically connected and connected to the output shaft 107 of motor I through the power output transmission clutch 801. The second gear 804 of the second power output transmission shaft meshes with the second gear 803 of the first power output transmission shaft, and the first gear 807 of the second power output transmission shaft meshes with the first gear 802 of the first power output transmission shaft. The second gear 804 of the second power output transmission shaft, the output shaft 805, and the first gear 807 of the second power output transmission shaft are connected through the power output transmission synchronizer 806.

[0067] like Figure 9 As shown, the control system of the hybrid tractor's power transmission system includes a main controller 901, a distribution box 902, an engine controller 903, a transmission system controller 904, a motor I controller 905, a motor II controller 906, and an energy management unit 907. The main controller 901 acquires information from the distribution box 902, engine controller 903, transmission system controller 904, motor I controller 905, motor II controller 906, and energy management unit 907 via a high-speed CAN bus; it also sends control signals to the distribution box 902, engine controller 903, transmission system controller 904, motor I controller 905, motor II controller 906, and energy management unit 907 via the high-speed CAN bus. The main controller 901 acquires information about the hybrid tractor's instruments and lighting via a low-speed CAN bus. The energy management unit 907 controls the energy storage unit 104, which supplies power to motor I 103, motor II 105, and the low-voltage battery through the distribution box 902.

[0068] After the hybrid tractor is started, the vehicle enters a system self-test. After the system self-test passes, the whole machine controller 901 acquires key signals, mode signals, position signals, torque signals, and speed signals. Based on the acquired information, the working status of the power output shaft, and the working status of the drive wheels, the whole machine controller 901 determines the working mode of the load end and sends control signals to the energy management unit 907, the power distribution box 902, the motor I controller 905, the motor II controller 906, the mechanical transmission system controller 904, and the engine controller 903.

[0069] Depending on the control method, the hybrid tractor system can be categorized into two power output modes: traction power output and rotational power output, resulting in different power flow manifestations.

[0070] (1) The traction power output of the wheels in 7 directions can be set in 7 operating modes: pure electric traction, engine independent traction, series coupled traction, parallel torque coupled traction, parallel speed coupled traction, hybrid coupled traction and energy recovery mode.

[0071] (2) Power output transmission: 8-direction rotational power output. The system can be set to 3 operating modes: pure electric drive, engine independent drive and parallel coupling drive.

[0072] Figure 10 The diagram shows the pure electric traction mode, in which motor II (EMII) is powered by the energy storage unit (EES) and independently supplies power to the central transmission mechanism 5 via a series gear transmission mechanism of the coupling device.

[0073] Figure 11 The diagram shows the engine-independent traction mode, in which the engine (ICE) independently provides power to the central transmission mechanism via the planetary gear ring, the planetary gears of the drive planetary set, and the planetary carrier of the planetary set in the coupling device.

[0074] Figure 12 The diagram shows a series-coupled traction mode, in which motor I is in generator mode, the engine provides power to motor I to generate electricity, and motor II is driven by electric energy to provide power to the central transmission mechanism.

[0075] Figure 13 The diagram shows a parallel torque-coupled traction mode. In this mode, motor I can output power, and the engine and motor I form a power coupling. Power is supplied to the central transmission mechanism through the planetary gear ring, the planetary gears of the drive planetary gear set, and the planetary carrier of the planetary gear set in the coupling device. Depending on the operating conditions, motor I can also generate electricity with excess power to supplement the energy storage unit.

[0076] Figure 14The diagram shows a parallel speed-coupled traction mode, in which the engine and motor II form a power coupling through the planetary gear mechanism in the coupling device, and jointly provide power to the central transmission mechanism.

[0077] Figure 15 The diagram shows a hybrid coupled traction mode, in which both motor I and motor II can output power, and the engine, motor I, and motor II form a power coupling to jointly provide power. Depending on the operating conditions, motor I and motor II can also use excess power to generate electricity, supplementing the energy storage unit.

[0078] Figure 16 The diagram shows the energy recovery mode in the traction power output operation mode. In this mode, the rotational power of the wheel is transmitted to motor II through the series gear transmission mechanism in the coupling device to generate electricity, and the generated electrical energy is used to supplement the energy storage unit to achieve energy recovery.

[0079] Figure 17 The diagram shows the pure electric drive mode in the rotary power output operation mode, where motor I provides power to the power output transmission mechanism independently.

[0080] Figure 18 The image shows the engine-independent drive mode, where the engine provides power to the power output transmission mechanism independently.

[0081] Figure 19 The diagram shows a parallel coupled drive mode, where the engine and motor I jointly provide power to the power output transmission mechanism.

[0082] The hybrid tractor can operate in a combination of modes based on power requirements and work methods. These modes, either independently or in combination, are divided into 11 combination modes, 7 traction modes, and 3 drive modes, as shown in the table below:

[0083]

[0084] When designing the control method for the hybrid tractor, the above mode can be selected according to the working environment and requirements to achieve control of the tractor's hybrid power system.

[0085] like Figure 20 As shown, during the operation of a hybrid tractor, the load-side operating mode is determined based on the output states of traction and rotational power, combined with acquired torque and speed signals and the energy storage capacity of the energy storage unit. (See figure.) The power demand at the wheel end is equivalent to the power of the power system. The power required at the power output shaft end is equivalent to the power of the power system. This represents the total power required by the power system. This represents the current state of charge of the battery. For storage batteries The upper limit; and These are the upper and lower limits of the economical speed range for the engine's mechanical connection; The rotational speed at the wheel end; This represents the lower limit of the economic range for the total power required by the engine's mechanical connections. When the total power required... Exceeding the lower limit of the economic range of total power required for diesel engine mechanical connection At that time, based on the rotational speed of the wheel end Determine the traction mode when the wheel end speed is... When the vehicle is within the upper and lower limits of the economic speed range of the diesel engine mechanical connection, a parallel torque coupling traction method with the engine and motor I jointly outputting power or an independent engine traction method is adopted; when the wheel end speed exceeds the upper and lower limits of the economic speed range of the diesel engine mechanical connection, a parallel speed coupling traction method with the engine and motor II jointly outputting power or a hybrid coupling traction method with the engine, motor I, and motor II jointly outputting power is adopted.

[0086] like Figure 20 The system selects a mode based on various conditions. When multiple modes meet the conditions, a strategy to minimize equivalent fuel consumption is used to switch between them. The formula for calculating the strategy to minimize equivalent fuel consumption, satisfying all system constraints, is as follows:

[0087]

[0088] In the formula: This represents the engine's actual fuel consumption rate. This represents the equivalent fuel consumption rate of the energy storage unit. Equivalent factor; This refers to the engine's output power; This refers to the output power of the energy storage unit. It has a low calorific value; This refers to the transmission efficiency of the energy storage unit.

[0089] The above description of specific embodiments is only for the purpose of helping to understand the technical concept and core idea of ​​the present invention. Although specific preferred embodiments have been used to describe and illustrate the technical solutions, they should not be construed as limiting the present invention itself. Those skilled in the art can make various changes in form and detail without departing from the technical concept of the present invention. These easily conceived changes or substitutions should all be covered within the protection scope of the present invention.

Claims

1. A hybrid power transmission system for a series-parallel hybrid tractor, comprising a power system (1), a coupling device (2), a central transmission mechanism (5), and a power output transmission mechanism (8); wherein the central transmission mechanism (5) and the power output transmission mechanism (8) are connected to the coupling device (2) and are respectively used to output traction power and rotational power; wherein the power system (1) comprises an engine (101), motor I (103), and motor II (105), characterized in that: The engine (101) is mechanically connected to the output shaft (107) of motor I. The output shaft (107) of motor I is connected to the coupling device (2) and the power output transmission mechanism (8), so that the engine (101) and motor I (103) can provide power independently or in a parallel coupled drive manner. The coupling device (2) includes a motor I shaft drive gear (202), a motor II shaft drive gear (201), a planetary gear mechanism, a series mode gear transmission mechanism, and a mode switcher (204); the motor I shaft drive gear (202) and the motor II shaft drive gear (201) are mechanically connected to the motor I output shaft (107) and the motor II output shaft (106), respectively; The drive gear (202) of motor I shaft meshes with the planetary gear ring (203) in the planetary gear mechanism, and the drive gear (201) of motor II shaft meshes with the driven gear (211) of motor II shaft connected to the sun gear (209) of the planetary gear set, so that the output shaft (107) of motor I and the output shaft (106) of motor II form a power coupling through the planetary gear set (212); the planetary carrier (208) of the planetary gear set (212) is connected to the output shaft (206) of the mode switching device through the mode switcher (204), and the output shaft (206) of the mode switching device is connected to the central transmission mechanism (5); The mode switcher (204) is connected to a series mode output gear (205) on one side of the output shaft (206) of the mode switching device. The driven gear (211) of the motor II shaft is connected to the series mode output gear (205) through the series mode gear transmission mechanism, forming an independent power transmission path between the output shaft (106) of the motor II and the output shaft (206) of the mode switching device. The series mode gear transmission mechanism includes a series mode input gear (210) and a series mode intermediate gear (207). The series mode input gear (210) meshes with the driven gear (211) of the motor II shaft and is mechanically connected to the series mode intermediate gear (207). The series mode intermediate gear (207) meshes with the series mode output gear (205). The mode switcher (204) is a dual-clutch structure, which can achieve mode switching by coupling transmission between the output shaft (107) of motor I and the output shaft (106) of motor II, or independent transmission of the output shaft (106) of motor II, through clutch connection with the planetary carrier (208) of the planetary gear set and the output shaft (206) of the mode switcher respectively.

2. The hybrid power transmission system for a tractor as described in claim 1, characterized in that: The motor II (105) is equipped with an electromagnetic locker that can lock the output shaft (106) of the motor II, so that the output shaft (107) of the motor I can independently drive the planetary gear (212) of the planetary gear set to transmit power to the planetary carrier (208) and the mode switcher (204) via the drive gear (202) of the motor I shaft and the planetary gear ring (203).

3. The hybrid power transmission system for a tractor as described in claim 1, characterized in that: The output shaft (107) of motor I passes through the output shaft (106) of motor II, so that the engine (101), motor I (103) and motor II (105) are arranged in a straight line.

4. The hybrid power transmission system for a series-parallel hybrid tractor as described in claim 1, characterized in that: The coupling device (2) is connected to the central transmission mechanism (5) via the transmission (3) and the transfer case (4); the transmission (3) includes a first shaft input gear (301), a two-speed synchronizer (302), a first shaft output gear (303), a transmission output shaft (304), a second shaft output gear (305), and a second shaft input gear (306); the first shaft input gear (301) is mechanically connected to the output shaft (206) of the mode switching device and meshes with the second shaft input gear (306); the first shaft output gear (303), the first shaft input gear (301), and the transmission output shaft (304) connected to the transfer case (4) are connected via the two-speed synchronizer (302); the first shaft output gear (303) meshes with the second shaft output gear (305); the second shaft input gear (306) is mechanically connected with the second shaft output gear (305), thereby realizing the speed change transmission from the first shaft input gear (301) to the first shaft output gear (303).

5. The hybrid power transmission system for a series-parallel hybrid tractor as described in claim 4, characterized in that: The transfer case (4) includes a transfer case input gear (401), a transfer case intermediate gear (402), a transfer case clutch (403), a transfer case front output shaft (404), and a transfer case output gear (405); the transfer case input gear (401) is mechanically connected to the transmission output shaft (304), the transfer case intermediate gear (402) meshes with the transfer case input gear (401) and the transfer case output gear (405) respectively; the transfer case output gear (405) is connected to the transfer case front output shaft (404) through the transfer case clutch (403).

6. The hybrid power transmission system for a series-parallel hybrid tractor as described in claim 1, characterized in that: The central transmission mechanism (5) includes a main reducer drive gear (501), a main reducer driven gear (502), a right half-shaft (503), a differential lock (504), a differential (505), and a left half-shaft (506). The main reducer drive gear (501) is mechanically connected to the transmission output shaft (304) and meshes with the main reducer driven gear (502). The main reducer driven gear (502) is mechanically connected to the differential (505). The right half-shaft (503) and the left half-shaft (506) are mechanically connected through the differential lock (504) and are respectively mechanically connected to the differential (505).

7. The hybrid power transmission system for a series-parallel hybrid tractor as described in claim 1, characterized in that: The central transmission mechanism (5) is connected to the wheel (7) through the final transmission mechanism (6). The final transmission mechanism (6) includes a final transmission ring gear (601), a wheel axle (602), a final transmission planetary carrier (603), a final transmission planetary gear (604), and a final transmission sun gear (605). The final transmission sun gear (605) is connected to the central transmission mechanism (5), the final transmission ring gear (601) is mechanically connected to the housing, and the final transmission planetary gear (604) meshes with the final transmission sun gear (605) and the final transmission ring gear (601) respectively. The final transmission planetary carrier (603) connected to the final transmission planetary gear (604) is mechanically connected to the wheel (7) through the wheel axle (602).

8. The hybrid power transmission system for a series-parallel hybrid tractor as described in claim 1, characterized in that: The power output transmission mechanism (8) includes a power output transmission clutch (801), a first gear (802) of a first shaft of power output transmission, a second gear (803) of a first shaft of power output transmission, a second gear (804) of a second shaft of power output transmission, a power output transmission output shaft (805), a power output transmission synchronizer (806), and a first gear (807) of a second shaft of power output transmission. The first gear (802) and the second gear (803) of the first shaft of power output transmission are mechanically connected and connected to the output shaft (107) of motor I through the power output transmission clutch (801). The second gear (804) of the second shaft of power output transmission meshes with the second gear (803) of the first shaft of power output transmission, and the first gear (807) of the second shaft of power output transmission meshes with the first gear (802) of the first shaft of power output transmission. The second gear (804), the output shaft (805), and the first gear (807) of the second shaft of power output transmission are connected through the power output transmission synchronizer (806).

9. The control method for a hybrid power transmission system of a series-parallel hybrid tractor as described in claim 1, characterized in that: During the operation of the hybrid tractor, the load-side working mode is determined based on the output status of traction power and rotational power, combined with the acquired torque signal, speed signal, and energy storage unit charge. When the total power demand exceeds the lower limit of the economic range of the total power demand of the diesel engine mechanical connection, the traction mode is determined based on the wheel speed. When the wheel speed is within the upper and lower limits of the economic range of the diesel engine mechanical connection, a parallel torque coupling traction mode with the engine and motor I jointly outputting power or an independent engine traction mode is adopted. When the wheel speed exceeds the upper and lower limits of the economic range of the diesel engine mechanical connection, a parallel speed coupling traction mode with the engine and motor II jointly outputting power or a hybrid coupling traction mode with the engine, motor I, and motor II jointly outputting power is adopted.

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